1. Field of the Invention
The present invention relates to an angular velocity sensor unit used in various electronic devices for the posture control, navigation and the like of movable bodies such as airplanes, automobiles, robots, ships and vehicles and an angular velocity sensor diagnosing device to which this angular velocity sensor unit is applied.
2. Description of the Related Art
A conventional angular velocity sensor causes, for example, a tuning fork shaped oscillator to oscillate, in order to electrically detect a strain of the oscillator resulting from a generated Coriolis force, and calculates an angular velocity based on an output from this oscillator. Normally, an angular velocity about one rotary axis can be calculated by one angular velocity sensor.
Oscillators used in angular velocity sensors of this type have various shapes such as tuning fork shapes, H-shapes and T-shapes. For example, as shown in FIG. 6, a tuning fork shaped oscillator 1 is constructed such that a bar-shaped shaft portion 4 is coupled to a U-shaped portion 3 including a pair of arm portions 2.
An arithmetic processing circuit for electrically detecting a strain of the oscillator 1 resulting from a Coriolis force and calculating an angular velocity through arithmetic processing is connected with this oscillator 1.
If such an angular velocity sensor is used, two angular velocity sensors need to be arranged to execute, for example, a vehicle posture control. If three axes orthogonal to each other in a vehicle are assumed to be a yaw axis, a roll axis and a pitch axis, the oscillator 1 of a first angular velocity sensor needs to be arranged such that the shaft portion thereof extends along the yaw-axis direction and the oscillator 1 of a second angular velocity sensor needs to be arranged such that the shaft portion thereof extends along the roll-axis direction.
By this arrangement, an angular velocity about the yaw axis can be calculated from the first angular velocity sensor and the one about the roll axis can be calculated from the second angular velocity sensor. Thus, a vehicle posture with respect to the yaw axis and the roll axis can be understood, enabling the posture control of the vehicle.
A failure judging circuit for judging an occurrence of a failure is provided for the first angular velocity sensor for calculating the angular velocity about the yaw axis. This circuit compares a pseudo-calculated angular velocity based on a vehicle speed, a steering angle of the vehicle, and acceleration and the like with the angular velocity calculated by the first angular velocity sensor, and makes a failure judgment based on a degree of coincidence between the two angular velocities.
For example, patent document 1 is known as prior art document information relating to the invention of this application.
Patent Document 1: Japanese Unexamined Patent Publication No. H02-297067
The above construction has had a problem that no failure judgment can be made for the second angular velocity sensor for calculating the angular velocity about the roll axis although it can be made for the first angular velocity sensor for calculating the angular velocity about the yaw axis.